Ch 2 · Permutations and Combinations

5 concept points · 5 formulas · 4 exam-critical points.

🧮 Formula sheet

1. nPr = n! / (n−r)!
2. nCr = n! / [r!(n−r)!]
3. nCr = nC(n−r)
4. nC0 + nC1 + ... + nCn = 2ⁿ
5. Circular arrangement (clockwise = anticlockwise): (n−1)!/2